Polyvinylidene fluoride (PVDF) is known to be a material which is difficult to cause to adhere substrate. Numerous solutions have been proposed, one of the most effective of which is to interpose at least one polymer which is compatible with PVDF between the substrate and the PVDF. It is apparent from the prior art solutions that the compatible polymer which can be used as the intermediate contains in its chain a branched carbonyl group in a chain of the type of: ##STR2## in which R is an alkyl radical.
Thus, methyl polymethacrylate, ethylene-vinyl acetate copolymers and ethylene-vinyl acetate copolymers to which a vinyl acetate polymer is added are used in the French Patents 2,457,180, 1,484,153, and 2,545,040, respectively.
The polymers which are immiscible with PVDF and contain ##STR3## in the polymer chain were tested as adhesion intermediates for PVDF. Thus, according to French Patent No. 2,347,402, polyurethane is used as the intermediate. Even though these polymers, containing carbonyl groups in the polymer chain, permit achievement of good adhesion of the PVDF to a substrate w ith which it is incompatible, a loss of adhesion is observed in the course of atmospheric aging, particularly at high humidity. It can be supposed that in the case of these immiscible polymers, the adhesion achieved with the PVDF is essentially due to the physical bonds; i.e., the hydrogen bonds at the interface of the two polymers, which bonds are eminently sensitive particularly to the water vapor present during any prolonged exposure to adverse weather conditions. Efforts to maintain good adhesion even in humid conditions has not been heretofore achieved.